This sounds like a technical term in mathematics. Can you give more context? It sounds like it has something to do with an polynomial or a power series, https://en.wikipedia.org/wiki/Power_series , or theory in computation about how rapidly the time for a calculation increases with the size of the numbers in the calculation. In physics, there is a term "order of magnitude," but it isn't shortened to "order." I'm thinking it is something like this: y = 6 + 5x + 7x^2 + 2x^3 and "5x" is of "order unity," but I'm not sure--that might be "degree" rather than "order."

I cannot respond in Chinese, but "it is of order unity" is a technical term. It means that it has a value of about 1. This means that it could have any value between 0.3 and 3.